A NULL pointer dereference in the function _TIFFmemcmp at tif_unix.c (called from TIFFWriteDirectoryTagTransferfunction) in LibTIFF 4.0.9 allows an attacker to cause a denial-of-service through a crafted tiff file. This vulnerability can be triggered by the executable tiffcp. https://nvd.nist.gov/vuln/detail/CVE-2018-17000
